This invention relates to a circuit for driving a signal meter for a receiver.
An IF amplifier for a receiver is often so constructed that a plurality of differential amplifiers are cascade connected in several stages and so that the differential output of a differential amplifier in the final stage is transmitted to a detection circuit in the next stage. A circuit for driving a signal meter according to the IF level in the IF amplifier is often designed, particularly when IC's are employed, to half-wave rectify the IF signal from the IF amplifier to thereby generate a driving voltage. However, in the conventional circuit thus constructed for driving a signal meter, when the center value of a driving output voltage is determined so that the voltage changes according to the input level of an antenna as indicated, for example, by an actual line a in FIG. 1, variations in the driving output voltage occur in the portion between actual lines b and c in FIG. 1 because of the variations in the performance of transistors, coupling capacitors and the like for use in the half-wave rectifier circuit. When the output voltage characteristics follow the actual line c in FIG. 1 because of such variations, a meter shows no indication even if the input level of the antenna becomes so high that the meter must read up-scale. Further, when the output voltage characteristics follow the actual line b in FIG. 1, the meter may indicate up-scale even though the input level of the antenna is zero, causing the offsetting of the meter.